Sustained winds are now nearing 60 mph (100 km/h) with higher gusts, and hurricane warnings may be required for Jamaica and the Cayman Islands.

Those areas currently are under hurricane and tropical storm watches.

The storm is about 260 miles (420 km) south of the Dominican Republic, heading west at about 23 mph.

In southern Trinidad, lightning struck two brothers who were out collecting rainwater, killing them instantly, Constable Shazeed Mohammed told The Associated Press. Heavy rains washed out roads and flooded villages in the area.

Chantal, which had reached tropical storm strength Wednesday before weakening Thursday, formed a more clearly defined center and had become better organized through the day on Friday.

The Atlantic has yet to see a hurricane this season, which began in June. Two other tropical storms, Allison and Barry, made landfall along the northern Gulf Shore of the United States with heavy rains and flooding.

Allison's 12-day march from Texas to New England left 35 people dead and caused more than $1 billion in damage.